Ethyltetramethylcyclopentadienyl derivative

The base-stabilized BH2 complex Cp Fe(CO)2(BH2-PMe3) (8.72, Fig. 24), has been synthesized via two routes photolytic methane elimination and salt elimination. The upheld 11B NMR chemical shift for this complex (8b -25.1) is indicative of a four-coordinate boron centre [98]. Likewise, the long Fe-B bond measured for the ethyltetramethylcyclopentadienyl derivative ( 75-C5Me4Et)Fe(CO)2(BH2-PMe3) [8.73, 2.195(14) A] and the very low carbonyl stretching frequencies (1932, 1869 cm-1), are as expected for a four-coordinate base-stabilized system [c.f. 2.129(3) A and 1958, 1899 cm-1 for Cp Fe(CO)2(BCl2 4pic), 8.42]. 

The method described here is based on that of Roe and Maitlis. An analogous dichIoro(f -ethyltetramethylcyclopentadienyl) derivative, [ CoCl2( f -C5Me4Et) 2], has been prepared by the extraction of CoCIj from [Co3CIe(i -CjMe4Et)2] in turn made from [Sn(ii-Bu)3(t -CsMe4Et)3 and CoCl2-... 

---